Ah, I think you may be right about IRC. Apple continues to want such things to be done via Push Notifications. Which is a pretty good solution for most things, though not all. E.g. I do IM (Windows Live) via Meebo, an app that uses notifications, and don't have any problems with it. IRC seems like it could work pretty well through such a system, too, though I don't know if anybody offers that service.

They specifically showed Skype as being able to run (continue calls or receive new ones) in the background through a very similar UI to the current built-in "Phone" app, so I think you'd be good on that one.